Treatment of acute experimental toxoplasmosis with investigational poloxamers.

Because of the limited chemotherapeutic approaches available to treat reactivated latent Toxoplasma gondii infection manifested as toxoplasmic encephalitis in AIDS patients, investigation of novel chemotherapeutic agents is warranted. Several poloxamers (nonionic block copolymers composed of a central hydrophobic chain of polyoxypropylene flanked by two hydrophilic chains of polyoxyethylene) were tested for their abilities to alter the course of acute infection with a highly virulent T. gondii in mice. The effect varied markedly with the length of the constituent chains of the copolymers. The most effective preparations were highly effective when administered after infection and afforded remarkable protection against 10 to 1,000 100% lethal doses of T. gondii. Protection was dose dependent, and multiple treatments were more effective than single treatment. These preliminary findings warrant additional studies to determine whether this novel form of antitoxoplasma chemotherapy may prove promising in the treatment or prevention of acute toxoplasmic encephalitis in humans.